Scuderi Group LLC’s novel split-cycle engine can be configured for gasoline, diesel and hybrid applications.

Imagine if you will, an engine that – under full-load conditions – has higher power, torque, efficiency and mileage ratings than equivalent displacement, state-of-the-art hybrid or turbocharged engines on the road today. Furthermore, imagine that engine exists today. Well, it does, and the automotive world could well be on the verge of a major paradigm shift.

The Scuderi Group first turned heads when it introduced its split-cycle engine at the 2006 SAE World Congress. Earlier this year, the company’s engine technology was validated in a full load (FL) study (i.e., the maximum attainable torque at any speed) by the industry-renowned Southwest Research Institute (SRI). The FL study says the core Scuderi split-cycle engine not only achieves higher efficiency than the best gasoline engines on the market, it shows that the engine has a higher torque than most of the conventional diesel engines in use today. SRI also says NOx emissions are substantially less than that of a conventional internal combustion engine.

In addition to the FL Study, SRI and Scuderi will be publishing two other studies on the Scuderi engine by mid-2008 – a part-load study at the recent 2008 SAE World Congress and an air-hybrid study by midyear. The air hybrid study will incorporate the results of full load and part load studies, but also integrate a compressed air storage tank used in the hybrid implementation, to compare the Scuderi air-hybrid efficiency levels to those of a conventional electric hybrid.

Attracted to validated performance efficiency improvements, along with lower displacements compared to conventional engines, several automakers and Tier I suppliers are actively collaborating with Scuderi.

Sal Scuderi, president of the Scuderi Group LLC, explains that the SRI study concluded that at full load:

1. The efficiency of the gasoline-fueled split-cycle engine would be around 37.5 percent, versus approximately 33 percent for conventional Otto cycle engines.

2. Torque levels would be about 50 percent higher than those of gasoline engines, taking the split-cycle engine into diesel territory in terms of torque.

3. The predicted NOx emissions are 50 percent to 80 percent less than that of a conventional engine, which will mean an even greater advantage in diesel applications.

“The results so far have exceeded our expectations,” says Scuderi. “What we’ve known all along through our initial modeling is finally validated. This report shows that the Scuderi split-cycle engine is poised to take the automotive industry into a greener, more fuel-efficient era.”

It’s Like Solving a Rubik’s Cube
Conceived by a team of fluid and thermodynamic experts, the Scuderi split-cycle and air-hybrid engine technology is designed to deliver a significant increase in performance, efficiency and environmental impact over today’s internal combustion engines. It accomplished these advances by targeting the heart of the engine, challenging conventional approaches to engine design in place for more than 120 years. Scuderi says, “It’s time to move engine technology into the 21st century.”

Key Benefits of the Scuderi Engine

1. Fuel efficiency improvements of 15 percent to 30 percent initially with further improvements possible. 2. Potential reduction of NOx emissions of 50 percent to 80 percent. 3. Lower average operating engine speed reduces engine wear and tear. 4. Design flexibility – more controllable parameters available for achieving enhanced or customized performance. 5. High torque at low rpm means higher power at lower engine speeds. 6. Compatibility with existing engine manufacturing processes and tooling. 7. Same total engine size (number of cylinders and displacement) as comparable conventional internal combustion engines. 8. Diesel engines can eliminate half the injectors and avoid costly aftertreatment systems. – B.C.

The first four-stroke piston engine was developed in 1876. This four-stroke piston arrangement is still the primary design of engines built today. Yet, despite immense efforts over the past century, engine efficiency has remained the same, operating at approximately 33 percent efficiency. This means that only one-third of the energy in each gallon of fuel is used – the rest is lost through friction and heat. With more than a billion engines currently in use worldwide, even small gains in efficiency will have a huge impact on the economy, dependency on foreign oil and the environment.

The heart of the internal combustion engine is a piston moving up and down in a cylinder connected to a crankshaft. Its simplicity makes improving performance almost impossible. Small improvements have proven difficult, and large improvements have been considered impossible.

While the industry invests millions and struggles for gains in the 1 percent range, the design of the Scuderi split-cycle technology pushes engine efficiency and performance to an entirely new level. The jump to 37.5 percent efficiency may seem minute to an outsider, but to industry insiders, the gain is phenomenal. Add in the up to 80 percent emissions reduction, and one can almost hear original equipment manufacturers (OEMs) salivating.

Sal Scuderi says the company’s proprietary and patented engine technology is adaptable to all fuel types, including diesel and gasoline automobiles, commercial vehicles and any other applications powered by internal combustion engines. Scuderi claims that an automobile with 30 miles per gallon would achieve almost 40 miles per gallon when equipped with the company’s engine.

By improving the heart of the engine, any piston engine – from motorcycles to trains – can be designed around this technology. The impact of this technology is simply staggering:

1. This technology not only saves energy but increases the power of an engine while significantly reducing its cost.

2. Vehicles will be able to exceed all current mileage and emission standards without compromising size or performance.

3. Consumers would save billions of dollars in fuel costs.

4. Reduction in emissions would be in the hundreds of millions of tons per year.

How It Works
The heart of conventional internal combustion engine design is a piston connected to a crankshaft, moving up and down in a cylinder through the four strokes of the Otto Cycle – intake, compression, power and exhaust strokes. In a typical four-stroke cycle engine, power is recovered from the combustion process in these four separate piston strokes within each single cylinder. This basic design has not changed for more than 120 years.

The Scuderi split-cycle engine design changes the heart of the conventional engine by dividing (or splitting) the four strokes of the Otto cycle over a paired combination of one compression cylinder and one power cylinder. Gas is compressed in the compression cylinder and transferred to the power cylinder through a gas passage.

The gas passage includes a set of uniquely timed valves, which maintain a precharged pressure through all four strokes of the cycle. Shortly after the piston in the power cylinder reaches its top dead center position, the gas is quickly transferred to the power cylinder and fired (or combusted) to produce the power stroke.

By splitting the strokes of the Otto cycle over a pair of dedicated compression and power cylinders, the design of each cylinder can be independently optimized to perform the separate and distinct tasks of compression and power. As a result, the split-cycle design provides more flexibility in how engines are built.

Many features that are known to be beneficial but impossible to implement in a conventional design can be implemented in the Scuderi split-cycle design. Its unique combination of having a powerstroke on every revolution, maintaining a precharged pressure in the gas passage and firing after top dead center in the power cylinder, produces several additional efficiency advantages. These include:

1. The power stroke can be made longer than the compression stroke to over-expand the gas for increased thermal efficiency.

2. The compression piston diameter can be made larger than the power piston diameter to supercharge the gas for increased power.

3. Compression and power cylinders can be independently offset to almost any angle for increased mechanical efficiency.

4. A faster burn rate, also known as combustion duration, is more than double that in a conventional engine.

5. There is a significant reduction in nitrogen oxide (NOx) emissions, which means the engine can run leaner and gain efficiency without the need for expensive add-on technologies.

6. Scuderi’s engine design does not require the use of exotic components and unique materials that would require a great deal of expensive retooling and/or redesign of an automotive production line.

7. Equipped with Scuderi’s Air-Hybrid feature, engines can realize even more efficiencies, notably doubling engine efficiencies and reducing emissions even further.

Stroke by Stroke
The basic concept of the Scuderi engine is to divide the four strokes of a standard engine over a paired combination of one compression cylinder and one power (or expansion) cylinder. These two cylinders perform their respective functions once per crankshaft revolution. A common misconception is that twice as many cylinders are required. This is simply not accurate. Because this engine fires every revolution instead of every other revolution, the number of power strokes produced is equal to the power strokes produced by two of the conventional piston/cylinder designs. —BC
On the intake stroke, a charge is drawn into the compression cylinder through typical poppet-style valves. During the compression stroke within the same cylinder, the charge is then pressurized and driven through the crossover passage, which acts as the intake port for the power cylinder. A check valve is used to prevent reverse flow from the crossover passage back into the compression cylinder, and likewise a poppet-style valve (crossover valve) prevents reverse flow from the power cylinder to the crossover passage. The check valve and crossover valve are timed to maintain pressure in the crossover passage at or above firing conditions during an entire four-stroke cycle.	Combustion occurs soon after the intake charge enters the power cylinder from the crossover passage. During the power stroke, the start of combustion occurs just after the power cylinder passes through its top dead center position (ATC). The resulting combustion drives the power cylinder down. Finally, exhaust gases are then pumped out of the power cylinder through a poppet valve, after which the cycle repeats.

Opportunity Knocks
While original equipment manufacturers (OEMs) around the world have been awaiting SRI findings, at this point the Scuderi Group is only releasing the complete data from the FL study to selected OEMs that have signed a nondisclosure agreement. The data will eventually be made public once the company’s worldwide patent applications have been published.

“We will begin ramping up our work on a diesel-fueled application of the split-cycle engine in the first quarter of 2008,” shares Scuderi. He notes that it looks like the split cycle engine may be able to address both NOx reduction and PM reduction without the same level of after-treatment systems required by current diesel engines.

He notes that already, the combination of lower engine-out emissions along with the reduced cost of the split-cycle engine compared to a conventional diesel (e.g., no turbocharger, half the fuel injectors, reduced after-treatment system) has also piqued the interest of light-duty vehicle OEMs worldwide.

The company was in attendance at the SAE World Congress in April to showcase its new developments and discuss future opportunities. With fuel prices soaring, unprecedented emissions standards in place around the globe, and OEMs seeking cost-effective alternative engine solutions, the interest was strong. For once, automakers, suppliers and consumers might all be winners.

Photos courtesy of The Scuderi Group.

Bob Chabot is an automotive writer based in Bedford, Texas. He may be reached at bobchabot2004@yahoo.com.